Lead-in arrangement



N. M. RUST Nov. 21, 1939.

LEAD- IN ARRANGEMENT Filed May 4, 1936 Patented Nov. 21, 1939 UNITEDSTATES PATENT OFFICE LEAD-IN ARRANGEMENT tion of Delaware ApplicationMay 4, 1936, Serial No. 77,726 In Great Britain June 8, 1935 2 Claims.

This invention relates to lead-in arrangements for wireles receivingsystems.

An important object of the invention is to provide a cheap low losslead-in arrangement suit- 6 able for use for short wave or for medium orlong wave broadcast reception, and wherein the construction isreasonably flexible mechanically and is such that the lead-in is of lowimpedance so that it may be directly connected to an associated aerialor aerials without any need for an interposed transformer at the aerialend.

Another important object of the invention is to provide an improvedlead-in arrangement adapted for use selectively with a plurality ofaerials each designed to present optimum efficiency over one of aplurality of wave length ranges.

The invention provides improved lead-in arrangements of the kind whereinthree conductors are used.

According to this invention a lead-in arrangement comprises threeconductors which are insulated from one another and are arranged to forma flexible or quasi flexible structure and either the outer pair ofconductors are utilized for energy transference and the inner conductorearthed or the inner conductor is utilized for energy transference andthe outer conductors earthed, the whole arrangement being such that thelead-in system as a whole is of low impedance whereby an it may bedirectly connected to an associated aerial or aerials without any needfor an interposed impedance transformer arrangement at the aerial end.

The invention is illustrated in the accompanying schematic anddiagrammatic drawing in which:

Fig. 1 illustrates a section through a preferred form of a threeconductor transmission line embodying the invention;

Fig. 2 illustrates diagrammatically a section through a transmissionline provided with apreferred type of covering;

Fig. 3 illustrates an arrangement for holding in position the spacingbeads along a. conductor; and,

Fig. 4 illustrates in diagrammatic form one method of utilizing thetransmission line in conjunction with an antenna and a radio receiver.

Referring to Fig. 1 the lead-in comprises three copper or similar stripsI, 2, 3 of which central conductor 2 is constituted by a strip which isgiven a slight twist and the two outer conductors I, 3, by wires whichfollow the twist of the strip. Small bead insulators l9 are threadedupon the wires I, 3, so that they come on either side of the strip andin this way relative insulation between the three conductors and correctrelative positioning of the three conductors is obtained, while at thesame time maintaining flexibility. This three conductor system is run inan outer 6 tube 20, e. g., a lead tube, or (preferably) as shown inFigure 2 a rubber tube 2| having an outer screen 22 of copper braid anda weather proof covering 23. The beads may be held longitudinally inposition upon the wire by slightly burring 10 the wire on either side ofeach bead as shown in Figure 3. The outside copper braid is in useearthed. Where this lead-in arrangement is used as a symmetrical twowire feeder the central strip 2 is earthed. Since by careful design 16the outer wire conductors may be made both physically andelectrostatically nearer the inner strip than the copper braiding themajority of the lines of force between the wire conductors and earthwill join between the wire conductors 20 and the strip rather thanbetween the wire conductors and the braiding, and the majority willtherefor out only the relatively low loss head insulators rather thanthe relatively high loss rubber outer tubing, so that di-electric losseswill 3 be kept low. Where the lead-in arrangement is used as a singlewire feeder, the central strip is used for energy transference and theouter wire conductors are earthed so that said wire conductors shieldthe central strip.

The lead-in arrangements described may be used as shown in Fig. 4 wherethe central strip conductor 2 is grounded at. the receiver and connectedat its other end to the middle of a symmetrical dipole in the event thatthe arrangement is used for short wave reception. The dipole may bemounted by means of poles I, I or the like. At the aerial end of thelead-in arrangement the two outer strip conductors l and 3 are connectedto the dipole symmetrically about the point of connection of the centralgrounded conductor 2. The outer conductors are led away from a centralconductor in tapered or, what might be referred to as, triangularfashion near the points of connection with the aerial. At the receiver45 end of the transmission line the outer conductors are connected toopposite ends of the primary of an input transformer 8 whose secondarywinding is connected between the grid and cath-= ode of a suitable inputtube 9 of the receiver. The tube 9 may be a frequency changer in thecase of superheterodyne receiver.

The invention is of wide application but the principal application isfor aerial lead-in arrangements for all wave ordinary broadcast recep- 5tion. Another important application of the invention is, however, totelevision reception.

The lead-in arrangements hereinbjeiore described are very suitable foruse as feeders for they are symmetrical, are of low impedance, and canbe suspended easily and cheaply or run quite close to the ground withoutneed for elaborate insulation. precautions. may, therefore, be used withadvantage as feeders in commercial electrical signalling systems.

Having now particularly described and ascertained the nature of theinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. In a lead-in arrangement, a central conductor comprising a flat stripof conducting material which is given a slight twist from end to end,

The said arrangements two outer conductors comprising wires positionedso as to follow the twist of said strip but on opposite sides thereof, asheath for enclosing said three conductors and bead insulator membersthreaded upon said wires at spaced apart points thereof so as to come oneither side of said strip, said bead insulators being shaped so as toprovide insulation between the three conductors and proper spacingbetween the conductors and the sheath while maintaining flexibility ofthe lead-in.

2. A lead-in arrangement as described in the next preceding claimcharacterized by that the bead insulators are held in position on thewires by burring provided on the wires on either side of each bead.

NOEL MEYER RUST.

